Electric machines are installed, as power sources, in various apparatuses. In applications to vehicles, for example, an electric machine is installed on a single base to function as a power source of an electric car or together with an internal combustion engine to function as a power source of an electric hybrid car.
In a case of an electric hybrid car, electric machines may be incorporated in a system in combination with an internal combustion engine via a planetary gear set to function as a generator and a motor if required. In this case, it is required to incorporate an internal combustion engine, an electric machine for power generation, and an electric machine for driving in the system together with a planetary gear set to provide an increase in size of the system, making it difficult to install in small sized cars.
JP2013-188065A (or Patent Literature 1) discloses an electric machine configured to combine different functions and function as a generator, a motor and a planetary gear set.
As shown in FIG. 9, the electric machine M described in JP2013-188065A includes a stator S with an armature winding C having 6 pole-pairs (pole-pair number A), a first rotor R1 with permanent magnets PM having 10 pole-pairs (pole-pair number P), and a second rotor R2 with magnetic paths MP having 16 poles (pole number H=A+P). This electric machine M is configured to be a magnetic modulation double-shaft motor, which uses the principle of magnetic modulation and makes three elements, including stator S, first rotor R1 and second rotor R2, to function as elements of a planetary gear set, i.e., a sun gear, a carrier and a ring gear.